Aspects of the disclosure relate to a sheet conveyor device for conveying a sheet along a predetermined conveying path, an image reading device including the sheet conveyor device, and an image forming apparatus including the sheet conveyor device.
There is known an image forming apparatus which includes a sheet stacker for stacking sheets discharged after having been conveyed along a predetermined path, and which can avoid curling-up of the tailing ends of the stacked sheets, as viewed in a conveying direction, by pressing the stacked sheets on the sheet stacker with a sheet retaining member.
With the provision of the sheet pressing member, even when the sheet curling to some extent is discharged to the sheet stacker, the tailing end of the sheet may be kept from curling up. It is, therefore, possible to prevent or avoid collision of a sheet (specifically, its leading end), which is subsequently to the sheet stacker, against the sheet having been previously discharged and stacked in a curled-up state.
Further, because such collision may be avoided, it is also possible to prevent or avoid, for example, a drawback called a corner folding (i.e., folding of a corner at the leading end of a sheet) that is otherwise caused in the subsequently discharged sheet upon the collision against the previously discharged sheet. In addition, because such collision may be avoided, the already discharged sheet may be prevented or avoided from being pushed out of the sheet stacker upon the collision.
However, when the weight of the sheet pressing member is too heavy, or when an urging force acting on the sheet pressing member is too strong, the sheet pressing member may be not swung upwards even with the sheet striking against the sheet pressing member when the sheet is going to be discharged to the sheet stacker.
In that case, as illustrated in FIG. 7A, a sheet 103 discharged to a sheet stacker 101 is abruptly bent downwards in its moving direction upon contacting with a sheet pressing member 105. Therefore, the leading end of the sheet 103 collides against the sheet stacker 101, thus possibly causing a drawback, such as the corner folding at the leading end of the sheet 103.
On the other hand, when the weight of the sheet pressing member is light, or when the urging force acting on the sheet pressing member is weak, the sheet pressing member is swung upwards with the sheet, discharged to the sheet stacker, striking against the sheet pressing member. In that case, the sheet may be avoided from being abruptly bent downwards in its moving direction, and hence the occurrence of the above-described corner folding can also be avoided.
However, when the weight of the sheet pressing member is too light, or when the urging force acting on the sheet pressing member is too weak, the sheet pressing member cannot sufficiently hold down the already discharged sheets. In that case, as illustrated in FIG. 7B, a position of the tailing end of an already discharged sheet 107 in the moving direction cannot be sufficiently displaced downwards, thus causing the problem that the subsequently-discharged sheet 103 is more liable to collide against the already discharged sheet 107.
Stated another way, a pressing force applied from the sheet pressing member and acting on the sheet tends to cause the problem in any of the case where the pressing force is set excessively strong and the case where it is set excessively weak. Accordingly, optimizing the pressing force applied from the sheet pressing member and acting on the sheet is very difficult from the viewpoint of design.